Compact valve-lifters

Abstract: Compact valve-lifters 104 are disclosed for overhead camshaft engines 100 with direct-acting valve gear 108 and for engines with indirect-acting valve actuation such as push-rod-actuated overhead valves. Two-step variable-lift and non-variable-lift valve-lifters are included as are roller and non-roller cam-follower types with various features in common.

Description: This invention relates to valve-lifters for internal combustion engines and the like. In particular, the invention concerns cam-actuated variable and non-variable lift, roller and non-roller type compact valve-lifters of both direct and non-direct acting types for overhead, in-head and in-block camshaft engines. PCT international patent application publication W091/12413 (Lotus) published 22 August 1991 discloses valve-lift control devices of various forms which provide variable valve-lift. In one embodiment, a lifter has a cylindrical high-lift outer cam-follower that engages a pair of spaced cams for high-lift valve actuation and a low-lift inner cam-follower that engages a central low-lift cam directly or through an intermediate follower member for low-lift valve actuation. The inner cam-follower is reciprocable in a bore of the outer cam-follower and directly actuates the valve through a hydraulic lash-adjuster. The outer cam-follower is reciprocable In a bore of an associated engine component and is selectively connectable to the inner cam-follower by locking means. These, when engaged, cause the inner cam-follower to move with the outer cam-follower, thereby actuating the valve in a high-lift motion determined by the profiles of the high-lift cams. EP-A-0468202 discloses a valve lifter in accordance with the pre-amble of claim 1. A valve lifter in accordance with the present invention is characterised over EP-A-0468202 by the features specified in the characterising portion of claim 1. The present invention provides a valve lifter that is roller actuated and in which the outer cam follower is maintained in proper alignment with the inner structure. This and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings, in which: Figure 1 is a transverse, cross-sectional, partially schematic view of an engine with indirect acting valve mechanism; Figure 2 is a cross-sectional view across a central axis of the valve-lifter shown in Figure 1, taken from the line 2-2 of Figure 1; Figure 3 is a cross-sectional view along the axis of the valve-lifter and an associated portion of a valve train taken from the line 3-3 of Figure 2 but shown with a different camshaft rotational position; Figure 4 is a cross-sectional view similar to Figure 3 but showing a second indirect-acting valve mechanism and valve-lifter Figures 4a and 4b are views similar to, and showing variations of, the embodiment of Figure 4; Figure 5 is a partially schematic cross-sectional view of an engine having direct-acting valve mechanism with a variable lift direct-acting valve-lifter ; Figure 5a is an enlarged cross-sectional view of a variable lift direct-acting valve-lifter similar to that of Figure 5; Figure 5b is a top view of the valve-lifter of Figure 5a; Figure 6 is a cross-sectional view across a central axis of the direct-acting valve-lifter shown in Figure 5a, taken from the line 6-6 of Figure 5a; Figures 6a and 6b are views similar to and showing variations of the embodiment of Figure 6; Figure 7 is a cross-sectional view of the direct-acting valve-lifter shown in Figure 5a, taken from the line 7-7 of Figure 5a; and Figures 7a and 7b are views similar to and showing variations of the embodiment of Figure 7. Referring now to Figures 1-3 of the drawings in detail, numeral 10 generally indicates an overhead valve, cam-in-block, reciprocating piston engine having push-rod/rocker arm type valve gear and showing one embodiment of the present invention. The engine includes a cylinder block 11 having at least one cylinder 12 clcsed by a cylinder head 14. The cylinder head carries at least one inlet valve 15 and one exhaust valve, not shown, controlling ports connecting with the cylinder. Each valve is biased closed by a spring 16 and is opened by valve gear or mechanism such as a rocker arm 18 actuated by a push-rod 19, a valve-lifter 20 and an associated camshaft 22. The exhaust valves may be actuated by conventional devices or by valve-lifters in accordance with the present invention, but, in the illustrated example, the valve-lifter for each inlet valve 15 is a two-step variable hydraulic valve-lifter (VHVL) 20 selectively actuated by a pair of spaced high-lift cams 23 and a central low-lift cam 24 located on the camshaft 22 between the high-lift cams 23. The valve-lifter 20 includes a high-lift outer cam-follower 26 actuated by the high-lift cams 23 and a low-lift inner cam-follower 27 actuated by the low-lift cam 24. The outer cam-follower 26 has a cylindrical annular body 28 that is reciprocable in a valve-lifter bore 30 of the engine block. A first annular end 31 of the body 28 engages the high-lift cams 23 whilst an opposite second annular end 32 includes a recess 34 in which a return spring 35 is seated. The first end 31 is preferably made as a separate plug that closes the open end of an annular hollow portion 36 of the body 28. This minimises the mass and allows the body 28 to be made of a different hardness or material than the end plug 31 which engages the cams 23. The body 28 also has a cylindrical outer surface 38 received in the valve-lifter bore 30 and a concentric cylindrical inner surface 39. The spring 35 preferably seats upwardly against a rotator bearing 40 which is mounted in the engine block 11 and facilitates rotation of the valve-lifter 20, which is desirable for low wear thereof. The low-lift inner cam-follower 27 is formed much like a conventional valve-lifter although of smaller diameter than those now in common use. It includes a hollow piston 42 with a closed end 43, an open end 44 and a cylindrical wall 46 reciprocably engaging the cylindrical inner surface 39 of the body 28. The closed end 43 selectively engages the central low-lift cam 24 of the camshaft 22. Cam-follower 27 further includes hydraulic lash-adjusting elements including a plunger 47, check-ball 48, ball-cage 50, ball-spring 51 and plunger-spring 52. A push-rod seat 54 mounts against the plunger 47 in a counterbore in the open end 44 of the piston 27. Lubricating oil flow to the push-rod and rocker arm through an orifice 55 in the seat 54 is controlled by a metering disk 56 retained by a retainer 58 in known manner. These features are found in many production valve-lifters. An annular oil groove 59 around the body 28 connects with a pressure oil gallery 60 in the engine block. Connecting oil passages 62, 63 in the body 28 and piston wall 46, respectively, feed oil from the groove 59 through slots in the plunger 47 to the lash-adjuster and to the hollow push-rod 19 for lubricating the rocker arm 18. Radial openings 64 in the body receive headed lock pins 66 biased outwardly by springs 67. Retaining pins 68 hold the lock pins 66 in the body 28. Flats 70 or other suitable recesses are provided on the piston 42 for engagement by the respective lock pins 66 when those pins are forced inwards. To prevent relative rotation of the body 28 and piston 42 and to maintain the lock pins 66 and flats 70 in alignment with one another, alignment means are provided such as a guide pin 71 fixed in the body 28 and engaging a guide groove 72 in the piston 42. In operation, pressure control means, not shown, are provided to selectively control the oil pressure in the oil gallery 60 to vary the valve-lift between low and high-lift functions and to provide adequate oil pressure for hydraulic lash-adjuster operation. With low pressure, the lock pins 66 are retracted and the inner and outer cam-followers 27, 26 are disengaged from one another. Thus, the inner cam-follower 27 engages and is controlled by the central cam 24 to move the valve in a low-lift motion and the outer cam-follower 26 idles by moving with the high-lift cams 23 but without any connection with, or effect upon, the valve motion. Increasing the oil pressure by the control means causes the lock pins 66 to move inwards and, when the cam-followers 26 and 27 are on the cam base circles, to engage the flats 70 to lock the inner and outer cam-followers together as shown in the drawings. The inner cam-follower 27 thus moves with the outer cam-follower 26 along the high-lift curve established by the high-lift cams 23 and the valve 15 is moved in a corresponding high-lift motion. Figure 4 illustrates another embodiment of engine with push-rod type valve gear in which each intake valve is actuated by an indirect-acting roller variable hydraulic valve-lifter (RVHVL) 74. As shown, in the illustrated embodiment, the lubricating, lash-adjusting, locking and alignment features of valve-lifter 74 are the same as or similar to those of the first described valve-lifter 20 so their description will not be repeated and, where needed, like numerals indicate like parts. The outer cam-follower 75 and the inner cam-follower 76 differ from the first embodiment in the provision of cam-engaging cam-follower rollers. An annular body 78 of the outer cam-follower 75 is extended to carry in slot-like recesses 79 a pair of spaced rollers 80 engaging spaced high-lift cams 82 of a camshaft 83. The rollers 80 may ride on bearings, such as needles, not shown, which are carried on axle pins 84 received in transverse bores 85 in the body 78. Similarly, a hollow piston 86 of the inner cam-follower 76 is extended to carry in a recess 87 a single cam-follower roller 88 engageable with a central low-lift cam 89 and rotatably carried on bearings, such as needles not shown, which ride on an axle pin 90. The pin 90 is received in a transverse bore 91 in the extended portion of the piston 86. The pin 90 may be press-fitted, staked or otherwise held fixed in the bore 91 in spaced relation with the pins 84. If desired, the rollers could be journalled directly on bronze pins or have other suitable bearings instead of the needle bearings referred to. In operation, because of the use of roller cam-followers 75, 76 suitable alignment means are needed to prevent rotation thereof about their reciprocation axis 94. Obviously, the rotator bearing 40 of the first embodiment is no longer needed. For the outer cam-follower 75, outer ends 95 of the axle pins 84 may extend beyond the body 78 into mating grooves 96 provided in an associated bore 98 of an engine block 99. Then means, as shown, such as pin 71 and groove 72 similar to the first embodiment may be used to prevent relative rotation of the inner and outer cam-followers 75, 76. Thus, the rollers 80, 88 are maintained square with the axis of the camshaft 83 and ride properly on their respective cams 82, 89. In other respects, the Figure 4 embodiment operates in the same manner as that first described. Figures 4a and 4b illustrate some variations of the second embodiment in the manner of aligning the inner and outer cam-followers. In Figure 4a, axle pins 84a have reduced diameter inner ends that extend beyond the inner surface 39 of the body 78 into grooves 72a formed in a modified piston 86a to maintain alignment of the cam-followers. A central roller axle pin 90a is held in openings in the piston 86a. In the variation shown in Figure 4b, flat inner ends of axle pins 84b extend inwardly of the inner surface 39 and engage flats 72b on a modified piston 86b to maintain cam-follower alignment. A central roller axle pin 90b is again retained in openings in the piston 86b. Figures 5-7 with added sub-letter views illustrate variations of still another embodiment wherein a two-step variable lift valve mechanism is provided in an overhead cam engine 100 having direct-acting cam-followers. As shown in Figure 5, the engine 100 includes a block, head and/or carrier component 102 supporting a camshaft 103 and a plurality of roller variable direct-acting hydraulic valve-lifters (RVDAH) 104c, only one being shown. The camshaft 103 includes a pair of spaced high-lift cams 106 and a central low-lift cam 107 for each of inlet valves 108 and/or exhaust valves of the engine that are actuated by an RVDAH lifter. In the engine shown, each valve-lifter 104c has a high-lift outer cam-follower 110 associated with the high-lift cams 106 and a low-lift inner cam-follower 111 associated with the low-lift cam 107. Detailed construction of the valve-lifter is best shown in the variation of valve-lifter 104 illustrated in Figures 5a, 5b, 6 and 7. The outer cam-follower 110 has an annular body 112 with a cylindrical outer surface 114 that is reciprocable in a bore 115 in the engine cam carrier or other component 102. The outer surface 114 extends along an upper head portion 116 of the body and an adjoining depending skirt portion 117. The head portion 116 also has a cylindrical inner surface 118 spaced concentrically within the outer surface 114 and terminates downwardly in a radial abutment in the form of a shoulder 119. Between the inner and outer surfaces 114, 118, are laterally-spaced recessed pockets 120 in which rollers 122 are located. The rollers 122 engage the cams 106 and are rotatably carried by suitable bearing means supported on axle pins 124, 124' held by locator pins 125 in transverse openings of the cam-follower head 116. Preferably, one of the pins 124' has an outer end 126 that extends outwardly of the outer surface 114 into a mating groove 127 of the associated bore 115. This prevents rotation of the cam-follower and maintains the rollers in alignment with their respective cams 106. The inner cam-follower 111 comprises a hollow cylinder 130 having a closed end 131 and a depending cylindrical outer wall 132 open at the other end. The closed end 131 is engageable with the central low-lift cam 107 to follow its lift curve. The outer wall 132 is received in the cylindrical inner surface 118 of the outer cam-follower 110 for reciprocation on a common axis 134 therewith. Grooves or flats 135 are engaged by inner ends 136 of the pins 124, 124' which extend inwardly beyond the inner surface 118 of the outer cam-follower to prevent relative rotation of the cam-followers. Within the follower cylinder 130, there is received a small hydraulic lash-adjuster or hydraulic element assembly (HEA) 138. This HEA includes a hollow piston 139 internally carrying a plunger 140 with a check-valve 141 and other elements similar to conventional HEA's although of smaller size in these preferred embodiments. Elements 50-52 of Figure 3 are of a generally similar character and function. A groove 142 may be provided on the plunger 140 to control oil leakage from the piston. The piston 139 directly engages the stem of the valve 108 for actuating it in an opening direction. A valve spring 143 acting against the valve and a fixed seat, not shown, in the engine biases the valve 108 in a closing direction. A concentric outer spring 144, acting between the shoulder 119 and a fixed seat, not shown, similarly biases the rollers of the outer cam-follower 110 against the high-lift cams 106. An arcuate groove 145 around the outer surface 114 of the body 112 receives oil from a gallery 146 in the component 102 and carries it through oil passages 147, 148 in the body 112 and cylinder 130 to deliver oil from the groove 145 to the interior of the cylinder for supplying oil to the lash-adjuster (HEA). Lock pins 150 (see Figure 7) carried in the body 112 of the outer cam-follower 110 are open to the groove 145. They co-operate with elements similar to openings 64, springs 67, retaining pins 68 and flats 70 of the embodiment shown in Figure 3 to lock the inner and outer cam-followers 110, 111 together or to release them in the manner described with regard to the Figure 3 embodiment. Oil pressure may be controlled in the manner described for that embodiment. Figures 6a and 7a show a variation of the third RVDAH embodiment wherein inner ends 136a of the axle pins 124, 124' are of reduced diameter to extend into grooves 135a of relatively narrow width in a modified cylinder 130a. This maintains alignment of the inner and outer cam-followers. A comparable variation is shown in the valve-lifter 104c of Figure 5 where the outer ends of the axle pins are of reduced diameter and engage narrower grooves in the sleeve 115 to prevent rotation of the valve-lifter in its bore. Figure 7b shows another variation, similar to that of Figure 2, wherein a guide pin 71b carried in the modified body 112 extends into a narrow groove 72b in cylinder 130b to maintain alignment of the cam-followers. In operation, camshaft rotation causes the high-lift cams 106 to actuate the outer cam-follower 110 on a full, high-lift curve whilst the low-lift cam 107 selectively actuates the inner cam-follower 111 on a partial, low-lift curve as determined by the cam profiles. When the oil pressure is controlled at a low level, the lock pins 150 are not engaged, as is shown in Figure 7, and the valve is moved through the low-lift curve by the low-lift cam 107 acting on the inner cam-follower 111 whilst the outer cam-follower 110 idles. When oil pressure is raised above a pre-set level, the lock pins 150 are actuated to lock the inner and outer cam-followers together so that the high-lift cams 106 control valve motion to follow the high-lift curve through the interconnected cam-followers 110, 111. The rollers 122 on the outer cam-follower 110 are effective to reduce the friction of the valve mechanism during operation on the high-lift curve and also during low-lift operation when the outer cam-follower 110 is moved in a high-lift idling motion against the bias of the outer return spring 144. Whilst it would be possible to also provide a roller on the inner cam-follower 111 to further reduce friction loss, this would require an increase in the size and mass of the inner cam-follower which may not be acceptable. Instead, the Figures 5-7 embodiment allows the HEA lash-adjuster 138 to be located between the rollers 122 to provide a compact and relatively low mass assembly. Since the friction created on the low-lift valve curve by the cam 107 moving the lighter low-lift cam-follower 111 only against the valve spring 143 is relatively low, this provides a preferable compact and efficient design for use in many overhead cam direct-acting valve gear applications. Whilst the invention has been described by reference to certain preferred and alternative embodiments and variations, it should be understood that numerous additional changes could be made within the scope of the invention claimed in the accompanying claims. For example, solid tappets or other lash-adjusters could replace the HEAs. Also, valve-lifters according to the invention may be applied to all or less than all of the intake and/or exhaust valves of the engine.

Claims: A valve-lifter (104) comprising a cam-follower (110) including a cylindrical body (112) with first and second annular ends and concentric inner and outer cylinder surfaces (114,118), the first annular end including a pair of laterally-spaced first cam-engaging rollers (122) ; and contact means intermediate the rollers (122) and adapted to engage a valve-actuating element of an associated valve train, in which the contact means is formed by an inner structure (130,139) reciprocally mounted within the body (112); characterised in that the inner structure (130,139) has a closed, cam-engaging end (131) opposite from the contact means; and in that the rollers (122) are mounted on shafts (124,124') having inner ends (136) extending beyond the inner cylinder surface (118) of the body (112) for engagement with associated means (135) of the inner structure (130,139), the shaft ends (136) and the associated means (135) comprising alignment means to prevent rotation of the body (112) relative to the inner structure (130). A valve-lifter (104) according to claim 1, in which the shafts (124,124') have outer ends (126) extending beyond the cylindrical outer surface (114) of the body (112) for engagement with alignment means (127) of associated support means (102) for co-operating with the shaft ends (126) to prevent rotation of the body (112) relative to the support means (102).

Inventors: DEMINCO CHRISTOPHER M, KUNZ TIMOTHY WILTON, NATHER SCOTT HENRY, PETERSON TIMOTHY JAMES, SAMALOT IVAN RAFAEL, SPATH MARK JAMES, DEMINCO, CHRISTOPHER M., KUNZ, TIMOTHY WILTON, NATHER, SCOTT HENRY, PETERSON, TIMOTHY JAMES, SAMALOT, IVAN RAFAEL, SPATH, MARK JAMES
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1994
Main classification: F01L13
IPC codes: F01L1, F01L13